# Basic concepts

**LIBSAFE** is a preservation system based in the OAIS, ISO 14721:2012 standard. The following are basic concepts in the LIBSAFE implementation, as to what refers to platform and system technical aspects.

**Disk**: storage unit, physical or logical, which ideally represents a stable, independent and individually accessible storage object, routable with a UNC path, in which the preservation system stores its information.

**Storage group**: disk set which makes up an independent data repository for the preservation system. Ideally, and according to the standard, the storage groups will be in different and distanced geographical locations, to withstand storage risks with guarantees.

**Dataformats**: different forms of representing data in the system. The use is to refer to file types associated with each format, normally recognizable from its extension; said extension  being the ending of the file name, and also being separated by a dot from the rest of the name and having a length of two to four characters. Examples for dataformats are PDFs, MS Word documents, JPEG compressed images.... and their most usual extensions would be .pdf, .doc or .docx, and .jpg.

**Dataformat characterizer**: a program that allows for simple identification of the data format of a file. The characterizers used by **LIBSAFE** are external modules, or wide use in the IT world, and specifically in the digital preservation community.

**Dataformat validator**: a program that will check that a file which is supposed to be of a specific dataformat, really complies with the format’s requirements. The validators used by **LIBSAFE** are external modules, or wide use in the IT world, and specifically in the digital preservation community.

**Dataformat evolver**: a program that copies a file from a dataformat to another, with the second copy retaining all the relevant information of the first, and the second dataformat being a more modern and accepted format than the origin dataformat. The evolvers used by **LIBSAFE** are external modules, and have been carefully chosen to guarantee the equivalence of the transformed files.

**Ingestion sanitizer**: a process to clean the package that makes an object from files and folders that are not part of its submission specification, but that do not disallow from its registry in the system.

**Ingestion check**: a process that verifies a condition in the object to be ingested, to guarantee compliance with the submission agreements, disallowing the object ingestion in case of non-compliance.

**Metadata filter**: a module or process that extracts metadata from a file, allowing for its processing by **LIBSAFE,** for later cataloging of the owner object.

**Datamover**: a tool to move files in the preservation system from one storage to another, automatically and without any effect on the created structures.

**Alarm**: a process by which **LIBSAFE** checks a particular condition and issues a notification on it. For example: a process to check for the start of ingestion jobs, which will send an e-mail to an administrator user when one is detected.

**Digital signature**: a tool that will guarantee the authenticity and integrity of the objects preserved in LIBSAFE over time.
